The present invention relates to air cylinders, and more specifically to a pressure gauge protection arrangement for an air cylinder.
A regular air cylinder 8 which holds a compressed gas for example oxygen, acetylene, ammonia, argon, etc., as shown in FIG. 12, is provided with a pressure regulator 9 for regulating the pressure of output gas for a safety application. The pressure regulator 9, as shown in FIGS. 13 and 14, comprises a base 91 having an inlet pipe 911 and an outlet pipe 912 at two opposite sides. Two pressure gauges 92 are mounted on the base 91 at the top side for detecting the pressure of input gas and the pressure of output gas respectively. A top cover 93 is covered on the base 91, defining a pressure chamber. The top cover 93 has a tubular projection 931, and a rotary knob 94 mounted on the tubular projection 931 for regulating the pressure of output gas. This arrangement has drawbacks. The pressure gauges 92 use front and back shells 921 and 922 to hold respective pressure sensors 923, dials 924, indexes 925 and glass plates 926 in place, and the shells 921 and 922 are fixedly fastened to respective coupling tubes 928 by screws 927, which coupling tubes 928 are respectively connected to the base 91. Because the shells 921 and 922 are made of a thin metal sheet by stamping, they tend to be deformed by an impact (see FIG. 15), causing the pressure sensors 923, dials 924 and indexes 925 of the pressure gauges 92 to be damaged. Because the pressure sensors 923 are sensitive, they tend to be damaged by an impact. In order to eliminate this problem, a metal shield may be installed and covered on the pressure gauges 92 for protection. However, when the metal shield is impacted, a stress is produced at the connecting area between the base 91 and the coupling tubes 928, causing the coupling tubes 928 to be deformed or broken.